Bsi bs en 00746 8 2000

NORME EUROPÉENNEICS 25.180.01 English version Industrial thermoprocessing equipment - Part 8: Particular safety requirements for quenching equipment Equipements thermiques industriels -

This British Standard, having

been prepared under the

direction of the Engineering

Sector Committee, was published

under the authority of the

Standards Committee and comes

into effect on 15 November 2000

 BSI 11-2000

ISBN 0 580 35980 8

Amendments issued since publication

National foreword

This British Standard is the official English language version of EN 746-8:2000 The UK participation in its preparation was entrusted by Technical Committee MCE/3, Safeguarding of machinery, to Subcommittee MCE/3/8, Thermoprocessing equipment - Safety, which has the responsibility to:

Ð aid enquirers to understand the text;

Ð present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed;

Ð monitor related international and European developments and promulgate them in the UK.

A list of organizations represented on this subcommittee can be obtained on request

to its secretary.

Cross-references

The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled ªInternational Standards Correspondence Indexº, or by using the ªFindº facility of the BSI Standards Electronic Catalogue.

A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application.

Compliance with a British Standard does not of itself confer immunity from legal obligations.

NORME EUROPÉENNE

ICS 25.180.01

English version

Industrial thermoprocessing equipment - Part 8: Particular safety

requirements for quenching equipment

Equipements thermiques industriels - Partie 8:

Prescriptions particulières de sécurité pour les

équipements de trempe

Industrielle Thermoprozeßanlagen - Teil 8: Besondere Sicherheitsanforderungen an Abschreckanlagen

This European Standard was approved by CEN on 22 November 1999.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member.

This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION

C O M I T É E U R O P É E N D E N O R M A L I S A T I O N

E U R O P Ä I S C H E S K O M I T E E F Ü R N O R M U N G

Central Secretariat: rue de Stassart, 36 B-1050 Brussels

© 2000 CEN All rights of exploitation in any form and by any means reserved

worldwide for CEN national Members.

Ref No EN 746-8:2000 E

7.2 Specific Information To Be Provided 287.3 Marking of quench equipment 297.4 User's information 30

7.6 Maintenance of the equipment 30

ANNEX ZA (INFORMATIVE) Clauses of this European Standard addressing

This European Standard has been prepared by Technical Committee CEN/TC 186 "Industrialthermoprocessing - Safety", the secretariat of which is held by DIN

This European Standard shall be given the status of a national standard, either by publication

of an identical text or by endorsement, at the latest by March 2001, and conflicting nationalstandards shall be withdrawn at the latest by March 2001

This European Standard has been prepared under a mandate given to CEN by the EuropeanCommission and the European Free Trade Association, and supports essential requirements of

EU Directive(s)

For relationship with EU Directive(s), see informative Annex ZA, which is an integral part ofthis standard

According to the CEN/CENELEC Internal Regulations, the national standards organizations

of the following countries are bound to implement this European Standard: Austria, Belgium,Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,

Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the UnitedKingdom

The working group that drafted this Part of EN 746 comprised experts from the followingcountries: France, Germany, Italy, Sweden and United Kingdom

This standard forms one part of a series safety standards covering Industrial

Thermoprocessing Equipment

The full list of parts of EN 746 is given below:

EN 746 Industrial Thermoprocessing Equipment

Part 1: Common Safety Requirements for Industrial Thermoprocessing

EquipmentPart 2: Safety Requirements for Combustion and Fuel Handling Systems

Part 3: Safety Requirements for the Generation and Use of Atmosphere gasesPart 4: Particular Safety Requirements for Hot Dip Galvanising

Thermoprocessing EquipmentPart 5: Particular Safety Requirements for Salt Bath Thermoprocessing

EquipmentPart 6: Particular Safety Requirements for Material Melting, Remelting and

Liquid Phase Maintaining Thermoprocessing EquipmentPart 7: Particular Safety Requirements for Vacuum Thermoprocessing

Equipment

Part 8: Particular Safety Requirements for Quenching Equipment

An assessment of the foreseeable risks arising from the use of the equipment was carried outwhen this standard was prepared.

The annexes A and ZA are informative

The EN 746-1 General Safety Requirements contains the common safety provisions anddevices for all types of industrial thermoprocessing equipment This part of the standarddetails in addition those extra safety requirements which need special attention against

quenching equipment

This European Standard is a type C standard as defined in EN 292:1991

The extent to which hazards are covered is indicated in the scope of this standard

This part of EN 746 gives the specific hazards and safety requirements that shall be provided

by the manufacturer for Quenching Equipment, whether it is used as an independent unit or anintegrated part of a plant

This part of EN 746 does not cover specific hazards and safety requirements for Salt Bath bathequipment used as a quenching means (see EN 746-5:2000)

This part of EN 746 does not cover the handling, storage, transport, disposal, transfer orregeneration of the quenching media and processed material outside the limits of the

equipment

This part of EN 746 standard applies not only to the normal operation of the equipment butalso to the safety of personnel and property when foreseeable faults occur in them

Examples of quenching equipment are shown in Fig 1 and Fig 2

NOTE: There are many variations in the design of quenching equipment Only two

examples of the various types are given in this text

This European Standard incorporates by dated or undated references, provisions from otherpublications These normative references are cited at the appropriate places in the text and thepublications are listed hereafter For dated references, subsequent amendments to or revisions

of any of these publications apply to this European Standard only when incorporated in it byamendment or revision For undated references the latest edition of the publication referred toapplies

EN 166 Personal eye-protection - Specifications

EN 292-1:1991 Safety of machinery Basic concepts, general principles for design

-Part 1: Basic terminology, methodology

EN 292-2:1991 Safety of machinery Basic concepts, general principles for design

-Part 2: Technical principles and specifications

EN 345 Specification for safety footwear for professional use

EN 346 Specification for protective footwear for professional use

EN 469 Protective clothing for firefighters - Requirements and test methods

for protective clothing for firefighting

EN 531 Protective clothing for industrial workers exposed to heat (excluding

fire fighters' and welders' clothing)

EN 614-1 Safety of machinery Ergonomic design principles

-Part 1: Terminology and general principles

EN 746-1:1997 Industrial Thermoprocessing Equipment

-Part 1: Common Safety Requirements for Industrial

Thermoprocessing Equipment

EN 746-2:1997 Industrial Thermoprocessing Equipment

-Part 2: Safety Requirements for Combustion and Fuel Handling

Systems

EN 746-3:1997 Industrial Thermoprocessing Equipment

-Part 3: Safety Requirements for the Generation and Use of

Atmosphere Gases

EN 746-5:2000 Industrial Thermoprocessing Equipment

-Part 5: -Particular Safety Requirements for Salt Bath

Thermoprocessing Equipment

EN 746-8:2000 Industrial Thermoprocessing Equipment

-Part 8: -Particular Safety Requirements for Quenching Equipment

prEN 1005-2:1998 Safety of machinery - Human physical performance

Part 2: Manual handling of machinery and component parts of

machinery

prEN 1005-3:1998 Safety of machinery Human physical performance

-Part 3: Recommended force limits for machinery operation

EN 1070 Safety of machinery - Terminology

EN 60204-1:1997 Safety of machinery Electrical equipment of machines

-Part 1: General requirements (IEC 60204-1:1997)

EN 61310-1 Safety of machinery Indication, marking and actuation

-Part 1: Requirements for visual, auditory and tacticle signals(IEC 61310-1:1995)

For the purposes of this standard the definitions given in EN 1070 apply

Additional definitions specifically needed for this standard are added below:

A quenching process where a liquid quenchant is pumped or flows by gravity over the surface

of the part to be treated

Components enter the quench medium in contact with the atmosphere contained in a fullyopen tank

A quenching process carried out in specially designed machines in which the hot component

is located between dies under pressure and held in position while the quenchant flows over it

A container of less than 1000 l capacity and with a surface area (open or covered) of less than

1 m2

A container of between 1000 l and 3000 l capacity and with a surface area (open or covered)

of not more than 2 m2

Table 1 shows the Hazard, Hazardous Situation, Preventative Measures and the VerificationMeans (as pointed out in clause 6) identified for the equipment type described in this part tothis standard.

4 Preventative measures

5 References

6 Verifi- cation means *)

EN 746-8:2000 5.8.1

5.8.2 5.8.3

1 and 2

2 EQUIPMENT USING QUENCHING OIL

5.11

1 and 2

water content in oil

1

2.1 Thermal Ejection of hot material causing

burns/scalds Water ingress - foaming Vacuum degassing Corrosion of bath, pipes, overflows

5 Provision of instructions to check water content in the oil

whose flash point is above the maximum working temperature of the tank (Temperature after quenching of the part)

1 and 2

immersion of a part does not lead to the maximum authorized temperature being exceeded The manufacturer shall indicate

to the user the maximum load characteristic (e.g.

4 Preventative measures

5 Referen ces

6 Verifi- cation means *)

5 rovide low level/high level detector/alarm, circulation monitor/alarm, temperature monitor/alarm (all

interlocked to heaters and feed system)

1

sized/colour coded valves

system shall be higher than the water pressure in the cooler

1 and 2

10 Instructions to user to carry out checks on flash point where necessary

1 and 2

temperature controller should give an indicating alarm in the event of controller failure (e.g gives

out regular checks on controllers

4 Preventative measures

5 Referen ces

6 Verifi- cation means *)

release in case of failure.

5.8 5.8.1 5.8.2

1 and 2

2.6 Materials and Substances

ventilation and adequate bath size

Contact with quenching medium

2 Provide instructions for choice of fluid, personal protective equipment, use of equipment

and use non-combustible ductwork

5.4 5.4.1 b)

1 and 2

protection for oil systems

working sprays/curtains/

chutes to extend 150 mm min below oil level in tank, baffle plates in larger tanks

5.12 5.12.4.1 5.8.3 a)

4 Provide instructions for fire prevention training

5.12 7.3

1

3 EQUIPMENT USING WATER/OIL EMULSIONS, SALT-SOLUTIONS AND POLYMERS

choice of emulsion formulations and the proper use of agitation/circulation systems

2 Design so that large tanks are fitted with detection alarm systems and the agitation/

4 Preventative measures

5 References

6 Verifi- cation Means *) 3.2 Harmful

substances

Burns or dermatitis from contact with

a) Emulsion b) Salt or caustic solutions c) Vapour

Provide information/instructions on the handling additions of anti- fungal, anti-bacterial and provision of protective equipment

4 EQUIPMENT USING MOLTEN LEAD OR LEAD ALLOYS

4.1 Thermal Burns by molten lead or lead alloys Provide instructions on use of

protective equipment

7.2.2 7.4

1

4.2 Harmful

substances

Inhalation, ingestion;

absorption of lead dust or fume

Design to enclose and extract fume from bath

5 EQUIPMENT USING FLUIDISED BED

by ejection of hot material

Provide instructions on the need

to avoid presence of combustible material in the area

EN 746-1:1997 5.11

1

1 Provide instructions/

information on handling harmful substances

7.4 7.2.2

1

6 NEGLECTING ERGONOMICAL PRINCIPLES

efforts causing impaired judgement

or poor visibility during charging

or discharging

The plant shall be designed in such a way that there is no hindrance for technical aids and possibility for good working postures

The manufacturer of vacuum thermoprocessing equipment shall be required to meet the

conditions detailed in this part to this standard

See EN 746-1 and EN 746-2 for general safety requirements relating to Thermoprocessing

Equipment

*) see Note to clause 6 for explanation of numbers

Machinery shall comply with the provisions of this clause They also shall comply with

EN 292:1991 for hazards which are relevant but not significant and which are not covered bythis standard

In addition equipment shall comply as appropriate, with other relevant parts of this standardlisted in clause 2 as well as with EN 292:1991 for hazards which are not covered in thesestandards

For requirements relating to signs and warning labels refer to EN 61310-1 for further

information

NOTE: The following preventative measures have been detailed to show how risks

arising from the hazards and hazardous situations detailed in table 1, clause 1

Quench tanks as defined in clause 3 shall be purpose-designed according to the quench

medium employed, conditions of use (temperature, pressure, etc.), the type of component to

be processed and the throughput for which they are intended The following design featuresshall be included

5.3.2 Minimum-Capacity

The designed minimum capacity and depth of the quench tank shall cater for the following:a) Displacement of the quenchant by the maximum load volume, including fixtures; (1)b) Expansion of the quenchant from the normal operating temperature up to the designatedmaximum; (1)

c) The inclusion of any baffles, extract conveyors, agitators, heating or cooling equipment,etc., inside the tank; (1)

d) Any build-up of sludge, loose scale or lost components in the tank between cleaningoperations; (1)

e) The provision of sufficient free board space to prevent slopping or overflow when theagitation and/or circulation systems are operating, and to cater for the retention of fire-fighting foam; (1)

f) The rate of heat input into the quenchant as determined by the throughput of work andthe presence and efficiency of any cooling system; (1)

g) The designer should pay regard to the placing and need of adequate guarding and otherphysical protection means; (1)

1) The top of the bath shall be at a minimum height of 0,9 m If this is not possiblethen a balustrade of height 1 m above floor with a mid rail shall be provided in theidentified area;

2) At the working position(s) the top of the bath or the balustrade rail can be lowered

to 0,7 m but only if the distance between the pot and balustrade is 0,2 m or more.5.3.3 Shape and construction

Consideration shall be given to the requirements of EN 746-3

In addition the design of the quench tank should take into account the foreseeable conditions

of use as follows:

a) The tank should have the minimum exposed liquid surface area; (1)

b) The materials of construction, thickness, method of fabrication and (where required)strength of reinforcement shall be suitable for the conditions of service (e.g

temperature, loading, corrosion, etc.); (1)

c) The shape and construction should facilitate effective inspection, cleaning, maintenanceand repair as required; (1 and 2)

d) Open tanks should be fitted with covers which can be safely removed or replaced Suchcovers should be in place when tanks are not in use to prevent contamination, ignition ofthe contents etc., and should be suitable for use as snuffer plates to exclude air in fire oremergency situations; (1 and 2)

e) Closed tanks shall be provided with adequate hatches for access, inspection,

maintenance and cleaning; (1 and 2)

f) Seals around pipework, etc., entering the tank below the liquid surface shall be suitablefor the quenchant in use and the operating conditions; (1)

g) Consideration should be given to whether a gravity-fed, vented dump tank facility in asafe location is needed If a dump tank is provided: (1 and 2)

1) Ensure that the quench tank is provided with covers and/or nitrogen blanketing toavoid air entry into the emptying quench tank and the starting of a fire on its oilysurfaces;

2) Ensure that it is connected to the base of the quench tank by a large-bore pipefitted with a flame trap and a quick release valve;

3) Any manually operated valve shall be operated in accordance with the instructionhandbook;

4) The design and operation of any automatically operated system shall take account

of the possibility of the hazard being transferred to the dump tank;

5) The design and operation shall ensure that, whenever a fire condition occurs, thetime for discharge should be not more than 5 minutes;

6) The valve shall be capable of operation in case of power failure and the overflowfacility recommended in 5.10.1 should be connected to the suggested dump tankpipework below the release valve;

7) Either manual or automatic systems shall be operable from a safe position;

h) Where vacuum oil quenching is undertaken a positive clamp shall be provided toprevent the door opening if the pressure exceeds 1 bar absolute; (1 and 2)

i) Pressure relief valves shall vent to a no danger zone (1 and 2)

When provided then they form part of the equipment

5.4.1 Local exhaust systems

Where fumes are generated by quenching operations to the extent that general ventilation ofthe workplace cannot reduce the local effect, then local exhaust shall be provided to reducethe hazard or nuisance level

a) Exhaust canopies, hoods, ductwork, etc., shall be non-combustible; (1)

b) Exhaust systems shall be designed as far as possible to prevent the accumulation ofcondensate (e.g water or oil) or shall be provided with drainage to prevent condensaterunning back to contaminate the quench tank; (1 and 2)

c) Ductwork for exhaust systems shall discharge at a safe point outside the building, i.e.away from air intakes, open windows, roadways, etc.; (1)

d) The construction of exhaust systems shall facilitate inspection, cleaning and

maintenance; (1)

e) Discharge points shall be adequately weatherproofed to prevent accidental

contamination of quenchants by water The weather-proofing shall not impede thedischarge of fumes; (1 and 2)

f) The exhaust system shall be designed to prevent the exposure of personnel to toxicfumes or vapour in excess of the appropriate exposure limits; (1)

g) Exhaust ductwork for oil quenching systems shall be fitted with fixed fire protectionsystems in accordance with 5.12.2; (1)

h) Exhaust ductwork shall be positioned such that any fire within the ductwork does notinvolve nearby pipework, services, electricity supplies or essential control systems; (1)i) Exhaust systems shall be designed to minimise contamination of plant or the building bycorrosive fumes, etc.; (1 and 2)

j) Emergency controls to shut down exhaust systems shall be located at accessible, safeand convenient point(s) (1 and 2)

5.4.2 General ventilation systems

Ventilation of the workplace atmosphere may be natural or forced, and shall be designed tominimise the effects of dust, fume, smoke, heat and toxic gases and keep these below theappropriate occupational exposure limits and/or reduce the nuisance value and improve theworking environment The operation of general ventilation systems shall not interfere with theeffective working of local exhaust systems Forced ventilation systems shall comply with theappropriate requirements of 5.12 (1)

NOTE: Fire ventilation is considered in 5.12

5.5.1 General

The following general points shall apply:

a) Careful consideration shall be given to the materials used in the manufacture of coolingsystems; (1)

NOTE 1: Typical problems include the following:

1) Corrosion;

2) Thermal cracking and sludging of hot oil;

3) Corrosion of welded joints

b) In order to minimise contamination of the quenchant, pipework joints shall not be madeinside quench tanks unless this is unavoidable; (1)

c) In order to minimise leakage, pipework joints shall be screwed, flanged or welded andnot brazed or soldered; (1)

d) Pipework and pumps in the cooling system shall be protected against the ingress of solidmatter by proper filtering; (1 and 2)

NOTE 2: This is especially important where oil is concerned and components may

carry scale, soot or salt into the quench

e) External cooling systems shall be located at a safe point away from risk of mechanicaldamage or involvement in fire Roof top cooling systems may require lightning andweather protection; (1)

f) Where appropriate, pumps shall be located at a safe point away from risk of mechanicaldamage or involvement in fire They shall be interlocked with heating,

agitation/circulation and quenching systems as appropriate to ensure that the coolingsystem is operating before quenching can take place; (1)

g) All pumps, motors and other electrical equipment associated with cooling systems shall

be located or protected to prevent contamination by fume, vapour, splashing or leakage,etc.; (1)

h) The discharge of cooled quenchant into the quench tank shall be positioned to minimisesplashing, especially when the quenchant level is approaching the set minimum;

(1 and 2)

i) Where a cooling system contains sufficient quenchant to cause overflow of the tanks,provision shall be made to prevent drainage of the cooling system into the quench tanksunder breakdown or emergency conditions; (1 and 2)

j) The temperature of the cooled quenchant shall be continuously monitored automatically

to ensure effective cooling and shall be interlocked to prevent further quenching if thecooling system fails; (1 and 2)

k) The offtake to the cooling system shall be taken from the upper part of the quenchantand returned cooled quench oil shall enter at a lower point (1)

5.5.2 Internal cooling coils (direct cooling)

The following shall also apply:

a) Cooling coils shall be located away from heating elements, areas of sludge accumulationand well clear of the position of quenched loads; (1)

b) Cooling coils using water as the coolant shall not be used in oil quench tanks (1)

a) External tracing shall be used where practicable in place of internal tracing where there

is a danger of water leakage causing contamination (e.g of quench oil or the furnaceatmosphere); (1)

NOTE: Where water-cooled jacketing is used, problems may arise from general

corrosion, and in particular from localised corrosion, at welds betweenthe jacket and the furnace structure This may be minimised by usingcorrosion-resistant materials, adding corrosion inhibitors to coolingwater, or ensuring that welds are always fully immersed Alternatively,oil can be used as the coolant

b) Where a jacket is fitted to a quench chute, then: (1)

1) The coolant should be the same as the quenchant;

2) The coolant supply and pump system should be separate from the main quenchantcooling/circulation system;

3) The jacket shall extend at least 150 mm below the minimum quench oil level Thiswill ensure that the chute is sealed from the atmosphere and also prevent localisedoverheating of the quenchant within the chute.

c) Provision shall be made to channel any condensate within an enclosed chamber awayfrom quench oil, or alternatively the temperature of the coolant shall be automaticallycontrolled to avoid such condensation (see 5.2 and 5.3.2) (1 and 2)

a) Steam and hot water shall not be used to heat oil tanks due to the risk of water-in-oilcontamination Both are suitable for heating water-based quenchants (see 5.2.7 EN 746-1:1997 and 4.4.4 and 12.3 of EN 60204-1:1997); (1)

b) External heating of the tank or pot is preferable for lead and fluidised beds; (1)

c) Immersion heaters shall be sheathed in a material of suitable resistance to corrosion andheat; (1)

d) Immersion heaters shall be located below the minimum quenchant level and be remotefrom areas with danger of mechanical damage by components being quenched and clear

of any build-up of debris and lost components Additional mechanical protection shall

be fitted where necessary; (1)

e) Immersion heaters shall have suitable surface loading power (e.g.W/cm2) and spacingthat will not cause local overheating; (1 and 2)

f) Heating systems shall be interlocked with the following: (1 and 2)

1) Agitation/circulation systems;

2) Quenchant fluid overtemperature detection system;

3) Quenchant cooling system;

4) Low liquid level detector;

g) Failure or inadequate operation of any of the system in f) shall shut down or preventoperation of the heating system; (1 and 2)

h) Heating elements should be fitted with a thermal cut-off set to isolate the power sourcewhenever the sheath becomes overheated in the event of the tank being emptied

(1 and 2)

5.8.1 Overhead Hoists

The following points should be noted:

a) Overhead hoists shall be of sufficient capacity to handle the heaviest foreseeable loads,including fixtures; (1)